Greenhorn requires advice on Sandboxing with cs-cart

I like to learn by experiment and have inheritted a cs-cart site (an old version 2.0). What is the best way to leave this site intact whilst I experiment? I am thinking an upgrade to v3 would be sensible but I couldn't see an option to download the trial for this. I have tried to edit blocks on my home page and had them disappear on clicking Save which has unnerved me. Is there no way to preview changes or Undo actions? (Ctrl+z is my good friend) The only thing I can do is restore to a previously backed up version, thus losing many hours of positive changes.

Do I need to purchase an extra storefront and have a test domain/subdomain? I realise I could have a copy of the website on my local computer for practising on but would this mean I need another cs-cart license?

Appreciate any ideas or guidance.

You can make a copy for development purposes in a subfolder for example. You might also want to skip version 3 and go straight to 4. The store importer is actually really good now.